

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: syy
 * Date: 2025-08-07
 * Time: 17:13
 */
public class MyLinkedList implements IList{
    static class ListNode{
        public int val;
        public ListNode prev;
        public ListNode next;

        public ListNode(int val){
            this.val=val;
        }
    }

    public ListNode head;
    public ListNode last;

    @Override
    public void addFirst(int data) {
        ListNode node=new ListNode(data);
        if(head==null){//这个思路很重要
            head=last=node;
        }else {
            node.next = head;
            head.prev = node;
            head = node;
        }
    }

    @Override
    public void addLast(int data) {
        ListNode node=new ListNode(data);
        if(head==null){
            head=last=node;
        }else{
            last.next=node;
            node.prev=last;
            last=last.next;
        }
    }

    @Override
    public void addIndex(int index, int data) {
        ListNode node=new ListNode(data);
        if(index<0||index>size()){
            return;
        }
        if(index==0){
            addFirst(data);
            return;
        }
        if(index==size()){
            addLast(data);
            return;
        }
        ListNode cur=findIndex(index);
        node.next=cur;
        cur.prev.next=node;
        node.prev=cur.prev;
        cur.prev=node;
    }

    private ListNode findIndex(int index){
        ListNode cur=head;
        while(index!=0){
           cur=cur.next;
           index--;
        }
        return cur;
    }

    @Override
    public boolean contains(int key) {
        ListNode cur=head;
        while(cur!=null){
            if(cur.val==key){
                return true;
            }
            cur=cur.next;
        }
        return false;
    }

    @Override
    public void remove(int key) {
        ListNode cur=head;
        while(cur!=null){
            if(cur.val==key){
                if(cur==head){
                    head=head.next;
                    if(head!=null){//这一步的作用是切断原本的head和新head之间的引用，在单向链表中没有prev所以不需要这么做
                        head.prev=null;//如果链表中只有一个节点，就不会执行这段代码
                    }
                }else {
                    cur.prev.next = cur.next;
                    if(cur==last){
                        last=last.prev;
                    }else {
                        cur.next.prev = cur.prev;
                    }
                }
                return;//已经找到了就结束
            }else{
                cur=cur.next;
            }
        }
    }

    @Override
    public void removeAllKey(int key) {
        ListNode cur=head;
        while(cur!=null){
            if(cur.val==key){
                if(cur==head){
                    head=head.next;
                    if(head!=null){
                        head.prev=null;
                    }
                }else {
                    cur.prev.next = cur.next;
                    if(cur==last){
                        last=last.prev;
                    }else {
                        cur.next.prev = cur.prev;
                    }
                }
            }
            cur=cur.next;//跟上面的区别是没有了else，无论有没有找到都让cur=cur.next
        }
    }


    @Override
    public int size() {
        ListNode cur=head;
        int len=0;
        while (cur != null) {
            len++;
            cur=cur.next;
        }
        return len;
    }

    @Override
    public void display() {
        ListNode cur=head;
        while(cur!=null){
            System.out.print(cur.val+" ");
            cur=cur.next;
        }
        System.out.println();
    }

    public void display(ListNode newHead) {
        ListNode cur = newHead;
        while (cur != null) {
            System.out.print(cur.val + " ");
            cur = cur.next;
        }
        System.out.println();
    }


    @Override
    public void clear() {
        ListNode cur=head;
        while(cur!=null){
            ListNode curN=cur.next;
            cur.prev=null;
            cur.next=null;
            cur=curN;
        }
        head=last=null;
    }




}
